feat(hub): group names unique per owner, shown as name@owner

A group's identity stays its UUID. What changes is that "the name is
unique" — until now an unenforced expectation — becomes real, scoped to the
owner account, and the owner's username is surfaced so two groups called
"photos" on different nodes can be told apart.

Hub:
- `groups` gains a functional unique index `uq_groups_owner_name` on
  `(admin_id, lower(name))` (model + migration c3d4e5f6a7b8). The migration
  pre-flights: if the data already clashes it aborts and lists the
  offending (admin_id, name) pairs rather than renaming anyone's group.
  meshbay.org checked clean.
- `create_group` trims the name, rejects blank (422) and an owner-scoped
  case-insensitive clash (409), with an IntegrityError backstop for the
  race, and returns `owner_username`.
- `owner_username` added to `/v1/groups/mine`, `GET /v1/groups` (local
  rows), `POST /v1/groups/{id}/join`, `GET /v1/admin/groups`.

SPA:
- new `static/group-name.js` — `<GroupName name owner [inline]>` renders the
  name with the `@owner` handle on a smaller grey line under it.
- used in the sidebar, the group-page header, Explore cards, the Admin
  groups table, and cross-group Search (via a widened `cacheGroupIndex`
  carrying the owner). Delete/leave confirmations show `name@owner` inline.
- federated Explore rows show `@<source_hub>` instead of an account.

Design record and the locked decisions: ~/next/groupnames.md (out of repo).
MNP unchanged. Tests: test_group_name_unique.py, test_group_name_migration.py.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018gKJ85aZyvEwarXMFzFEwi

1 files changed, 8 insertions, 3 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/group-page.js b/packages/meshbay-hub/src/meshbay_hub/static/group-page.js
index 470f169..4ebe5a7 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/group-page.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/group-page.js
@@ -9,6 +9,7 @@ import {
   HUB, session, cacheGroupIndex, hubFetch, ensureFreshToken, _loadBundleKey,
 } from './hub-client.js';
 import { visibleApps } from './apps.js';
+import { GroupName } from './group-name.js';
 import { FilePreview } from './files-app.js';
 import { VideoPlayer } from './video-player.js';
 import { MusicPlayerBar } from './music-player.js';
@@ -160,7 +161,8 @@ function GroupPage({ groupId, group, token, username, userId, userPrefs,
     setEntries(fresh);
     if (indexMsg.dirs) setNodeDirs(indexMsg.dirs);
       if (indexMsg.roots) setNodeRoots(indexMsg.roots);
-    cacheGroupIndex(groupId, group ? group.name : groupId, fresh);
+    cacheGroupIndex(groupId, group ? group.name : groupId,
+                    group ? group.owner_username : null, fresh);
   }, [groupId, group]);
 
   // additions/deletions/updates (daemon.py _broadcast_index_change, once
@@ -181,7 +183,8 @@ function GroupPage({ groupId, group, token, username, userId, userPrefs,
       const keptIds = new Set(updated.map((e) => e.id));
       const additions = (deltaMsg.additions || []).filter((e) => !keptIds.has(e.id));
       const fresh = updated.concat(additions);
-      cacheGroupIndex(groupId, group ? group.name : groupId, fresh);
+      cacheGroupIndex(groupId, group ? group.name : groupId,
+                    group ? group.owner_username : null, fresh);
       return fresh;
     });
   }, [groupId, group]);
@@ -493,7 +496,9 @@ function GroupPage({ groupId, group, token, username, userId, userPrefs,
       <div class="group-header">
         <div>
           <h2 style="margin-bottom:${group && group.description ? '4px' : '0'}">
-            ${group ? group.name : t('group.default_name')}
+            ${group
+              ? html`<${GroupName} name=${group.name} owner=${group.owner_username} />`
+              : t('group.default_name')}
           </h2>
           ${editingDesc
             ? html`